A shortage of trained staff and investigative technology has created a back-log of up to six years in garda inquiries into computer crime, including online child abuse.

The delays have resulted in some cases being dropped on the instructions of the Director of Public Prosecutions.

However, senior Garda officers are confident that the backlog will be reduced to two years by the end of 2016.

This is regarded as an acceptable period within the legal framework and will not interfere with potential prosecutions. Gardaí say the delays stretching back six years to 2010 apply only to a handful of cases while a couple of dozen cases date back to 2011.

Officers are reluctant to reveal figures but admit the relevant unit has been swamped by a huge growth in the internet crime area, including complaints about child abuse, in recent years without the matching increases in resources necessary to deal with the overload.

They say they must prioritise cases at present to ensure that the most serious and urgent inquiries are dealt with immediately and staff are at full stretch to limit the impact of the shortfall in numbers.

It is expected that additional staff will be allocated to the Computer Crime Investigation Unit (CCIU), which is part of the Garda National Fraud Bureau, after competitions for places are completed.

Its role is to investigate cybercrime, take part in international liaison with other law enforcement agencies and forensically examine all seized computer devices for a wide range of criminal cases, including child abuse and child porn.

Two pilot CCIUs have been set up in New Ross, Co Wexford, and Ballincollig, Co Cork.

A new structure will result in the unit being headed by a detective superintendent with two detective inspectors, splitting cyber crime from computer forensic examination, and each supported by additional gardaí and trained civilian staff.

Illegal

A senior Garda officer said the CCIU had been in existence for more than 20 years and had achieved many successes in detecting crimes such as computer-related fraud, online paedophilia and illegal trading over the 'darknet'.

Those successes include playing a key role in solving high-profile cases such as the murder of Rachel O'Reilly and the Graham Dwyer investigation.

It has also built up significant experience and expertise, with many of its people regarded externally as experts in their fields.

The officer said the restructuring would also ensure the unit had the capacity and capability to deal with current and future volumes of work.

Members of the CCIU work closely with the recently formed National Protective Services Bureau and personnel from the two units took part in an international training course, hosted earlier this year in Dublin by the FBI and the Garda.

The Protective Services Bureau's remit encompasses the investigation of sexual crimes against children, human exploitation and domestic violence and is under the control of a chief superintendent.